Process for freeing stuck drilling tools



.etsais v a dp i United States Patent PROCESS FOR FREEING STUCK DRILLING TOOLS Ferdinand H. D. A. Trusheim, Steimbke Kries Nienburg, Weser, Germany, assignor to Shell Development Company, New York, N.Y., a corporation of Delaware No Drawing. Application July 16,. 1956. Serial No. 597,877

Claims priority, application Germany July 21, 1 955 9 Claims. (Cl. 166-22) The present invention relates to a method for disintegrating agglomerations, debris or cuttings of earth formations encountered in well-drilling operations, and pertains to a process for freeing tools used in drilling, treating or testing boreholes, particularly boreholes which have been or are being drilled in exploring for or producing petroleum or natural gas.

It often happens in well-drilling operations that the drilling tool, e.g the drill string and the bit, sticks in the well and cannot be pulled up again. It may also happen in well testing, e.g., in acoustic or electric testing of boreholes. already drilled, or in treating these boreholes, such as in acid treatment, or in inserting packers, etc., that the tool being used becomes stuck.

In. such. cases attempts are made at freeing the tool by injectingacid, e.g. hydrochloric acid, into the well. If the tool has become jammed in a limestone layer, there is a possibility of succeeding in this way. However, an acid treatment is of no use for disintegrating a layer of clay, and is of little value in many other earth formations containing substantial amounts of clay, i.e., 10 percent clay or more.

It is therefore a primary object of this invention to provide a method for freeing a stuck tool used in the drilling, testing, treatment or production of wells.

A further object of the present invention is to provide a method for freeing a well drilling tool which has be come stuck in earth formations, particularly those formations containing clay in substantial amounts.

Another object of this invention is to provide a method 'for cleaning out well pumps, wire screens or slotted liners at the bottom of a well which have become clogged with disintegratable earth particles.

Other objects of this inventionwill' be understood from the following. description of the invention. According to. the invention, a borehole in which the .tool has become stuck is treated with hydrogen peroxide gas-bearing zone. In the event that an oil or gas-bearing zone. has.- beendrilled through, the concentration of, hy-

drogen peroxide used should not exceed percent from The present method may be practicedgby positioning in 2,000,020 Patented Aug. 18, 1959 In carrying out the treatment according to the invention, it is often an advantage to introduce into the borehole, or to cycle through the borehole, either together with the hydrogen peroxide solution or afterwards, a buffer liquid, preferably a liquid which is immiscible 'or only slightly miscible with hydrogen peroxide and does not react with hydrogen peroxide or only slightly, so that the hydrogen peroxide arrives, as nearly as possible, in the desired concentration to the place of damage in' the borehole. Carbon tetrachloride may be used, for example, as such a buffer liquid. It is preferred that a quantity of buffer liquid be placed both in front of and behind, the hydrogen peroxide solution so as to isolate it during circulation in the borehole in a manner well known in the field of well drilling. Instead of circulating the; hydrogen peroxide into position, it may be lowered into the borehole in any suitable container such as a bailer on a wire line in a manner well known in the art the container being opened or dumped after reaching the desired spot.

If' highly concentrated hydrogen peroxide is used, the buffer liquid chosen may also be Water or another liquid which is miscible with hydrogen peroxide, but does not react with it, or does so only slightly. In this case, despite the unavoidable mixing with the buffer liquid, a sufliciently high concentration of hydrogen peroxide can likewisebe obtained at the place of damage in the borehole. 1 {The use of a buffer is often very desirable, as otherwise the hydrogen peroxide, might react with any clay present in suspension or otherwise in the well while on example, /2 percent by weight of a caustic soda solution, together with /2 percent by weight of soda, calculated ,on the weight of the hydrogen peroxide.

. ln eleaning Well screens orliners by disintegrating rock materials that clog said liners,-sufiicient hydrogen peroxideispreferably put in the well to fill the liner and the boreholeoutside the liner.

The, invention is; ftuther illustrated by the following tests. 'i i i Example 1 1A, Platte-m s i be wn 0 p n y weight water) was-treated with an' aqueous '15 percent-hydrogen peroxide solution at 15 C. at atmospheric pressure. The

mass disintegrated in approximately 15 minutes; in water, however, an identical mass only disintegrated very slowly.

A. portion of the same mass was also treated at a pressure of atm. with a 15 percent hydrogen peroxide solution. The treatment was carried out at 50 C., i.e.

under borehole conditions, and the mass entirely disin-' No disintegration could be no-.

tegrated in 45 minutes. ticed with corresponding treatments of portions of the plastic mass with water.

An improved effect can often Example 2 Talang Djimar clay was treated at normal pressure and temperature once with water and a second time with a 1 5 percent hydrogen peroxide solution. No disintegra tron occurred with water, whereas with hydrogen peroxide the clay disintegrated within a short time.

Example 3 ide plus sodium carbonate but without hydrogen peroxide,

gave no result. With the treatment with a percent hydrogen peroxide solution only, the cuttings disintegrated more slowly than with sodium hydroxide and sodium carbonate added. r

-I claim as my invention:

v 1. A method of treating formations and earth material containing a substantial amount of clay encountered in well drilling operations which comprises introducing a quantity of hydrogen peroxide into a borehole drilled into the earth, positioning said quantity of hydrogen peroxide 10 percent adjacent thelocation to be treated, and maintaining said hydrogen peroxide in contact with the borehole Wall at said location for at least 15 minutes until at least a portion of said earth material has disintegrated.

3. A method of treating formations and earth material containing asubstantial amount of clay encountered in well drilling operations which comprises pumping under pressure a quantity of hydrogen peroxide into a borehole drilled into the earth, positioning said quantity of an aqueous hydrogen peroxide solution having a concentration of at least 10 percent adjacent the location to' be treated, and maintaining said hydrogen peroxide in contact with the borehole wall at said location for at least 15 minutes until at least a portion of said earth material has disintegrated.

4. A method of freeing from earth agglomerations c0ntaining a substantial amount of clay a stuck tool used in well operations, said method comprising introducing a quantity of hydrogen peroxide into a borehole drilled in 'the earth, positioning said hydrogen peroxide adjacent said stuck tool, and maintaining said hydrogen peroxide.

in contact with the borehole wall in said position for at least 15 minutes until at least a portion of said earth agglomerations adjacent said tool has disintegrated.

5. A method of freeing'from earth formations containing a substantial amount of clay a stuck tool usedin well "operations, said method comprising introducing a quantity of an aqueous hydrogen peroxide solution having a concentration of at least 10 percent into a borehole drilled in the earth, positioning said hydrogen peroxide adjacent said stuck tool, and maintaining said hydrogen peroxide in contact with the borehole wall in said position for at least 15 minutes until at least a portion of said earth formations adjacent said tool has disintegrated.

6. A method of freeing from earth formations a stuck tool used in well operations, said method comprising introducing a predominant quantity of hydrogen peroxide together with minor quantities of a caustic solution and an inorganic salt into a borehole drilled in the earth, positioning said hydrogen peroxide adjacent said stuck tool, and maintaining said hydrogen peroxide in contact with the borehole wall in said position until at least a portion of said earth formations adjacent said tool has-disintegrated.

7. A method of freeing from earth formations containing a substantial amount of clay a, stuck tool used in well operations, said method comprising introducing a predominant quantity of hydrogen peroxide together with minor quantities of a caustic soda solution and sodium carbonate into a borehole drilled in the earth, positioning said hydrogen peroxide adjacent said stuck tool, and maintaining said hydrogen peroxide in contact with the borehole wall in said position for at least 15. minutes until at least a portion of said earth formations adjacent said tool has disintegrated.

8. A method of cleaning disintegratable materials containing a substantial amount of. clay from a liner used in the production of wells, said method comprisingintroducing into the well and positoning in saidliner located in a well an amount of hydrogen peroxide sufficient to fill said liner, and maintaining said hydrogen peroxide in said position for at least 15 minutes until at least a portion of the materialinsaid liner has disintegrated. j

9. A method of cleaning disintegratable materials containing a substantial amount of clay from a liner used in the production of wells, said method comprising introducing into the well and positioning in said liner located in a well an amount of hydrogen peroxide sufficient to fill said liner and the well outside the liner, and maintaining said hydrogen peroxide in said position for at least 15 minutes until at least a portion of the material in said liner has disintegrated.

References Cited in the file of this patent UNITED STATES PATENTS Canada Apr. 10, 1951 OTHER REFERENCES. ,Well Completion Practices,jpart ,3 (of four), Washing, by Dr. Carrol M. Beeson, World Oil, January 1950.

Hackhs Chemical Dictionary, edition, by Grant. (Page 633 relied upon.) i s 1 h r 

1.A METHOD OF TREATING FORMATIONS AND EARTH MATERIAL CONTAINING A SUBSTANTIAL AMOUNT OF CLAY ENCOUNTERED IN WELL DRILLING OPERATION WHICH COMPRISE INTRODUCING A QUANTITY OF HYDROGEN PEROXIDE INTO A BOREHOLE DRILLED INTO THE EARTH, POSITIONING SAID QUANTITY OF HYDROGEN PEROXIDE ADJACENT THE LOCATION TO BE TREATED AND MAINTAINING SAID HYDROGEN PEROXIDE IN CONTACT WITH THE BOREHOLE WALL AT SAID LOCATION FOR AT LEAST 15 MINUTES UNTIL AT LEAST A PORTION OF SAID EARTH MATERIAL HAS DISINTEGRATED. 